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Old 06-05-2019, 18:33   #136
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Re: Yanmar SB12 Using Oil

Hard to say on the oil color. It was pretty dark brown but somewhat white from being mixed with water. The oil in the motor is always black - even immediately after changing it! I called the hauler today and set a launch date in the first week of June. I'm confident I'll be ready!
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Old 07-05-2019, 06:58   #137
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Re: Yanmar SB12 Using Oil

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Hard to say on the oil color. It was pretty dark brown but somewhat white from being mixed with water. The oil in the motor is always black - even immediately after changing it! I called the hauler today and set a launch date in the first week of June. I'm confident I'll be ready!
Our engine oil was instantly black as well before rebuild but now with better liner & new piston & rings it's somewhat slower to turn black. I'd guess there's 2 reasons for that, more complete fuel burn with higher compression & less blowby. It may improve in that department on yours after she's run in.
Looking fwd to June update
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Old 07-06-2019, 21:05   #138
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Re: Yanmar SB12 Using Oil

The boat got launched Monday the 5th. I've not gotten the mast stepped yet, but hope to do so tomorrow, and so I've not really motored the boat very far - just the mile to the club from the launching ramp and a couple of runs from the mooring to the dock.

The motor is running very well. It is smoother than I remember and it starts on the very first compression cycle. The knot-very-accurate meter shows 6kn at 2700 rpm and 6.5kn at 3000. I think that is a bit faster than it has been before. I won't claim any increase in speed until I can fully check things out with a GPS. (It seems to me that at any given RPM it shouldn't be any faster than before.) I have no report on the oil consumption yet - I've not even checked it - but I will start monitoring it as soon as I start putting some real time on the engine. There are no obvious oil leaks or other problems.

I'm hopeful this old motor is ready for another forty years!
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Old 07-06-2019, 21:43   #139
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Re: Yanmar SB12 Using Oil

Sounds extremely promising. Particularly like the part about starting on first compression stroke. Thats how ours behaved after rebuild & requires zero throttle advance now either.
Maybe the added speed is from clean hull on launching? I'd expect a slightly lower throttle setting for the same revs but yes same revs same speed.
Well you must be feeling quite pleased with your project. Good chance it will do another 40 years
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Old 08-06-2019, 05:36   #140
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Re: Yanmar SB12 Using Oil

Sadly, its highly likely that I won't. I'd be 107!
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Old 08-06-2019, 20:18   #141
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Re: Yanmar SB12 Using Oil

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Sadly, its highly likely that I won't. I'd be 107!
yes i know the problem but cyborgs aren't far off! We mite be uploads :-)
If not it will hammer someone elses bum & assault their eardrums & they will grow to love it. lol ( duno why we do must be masochists suffering from Stockholm syndrome)
Dont forget to change oil soon to get rid of any honing grit. Looking forward to update on oil consumption. I'd wager a bit that you've cracked it.
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Old 20-06-2019, 14:05   #142
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Re: Yanmar SB12 Using Oil

I now have three hours on the engine. It continues to run very well and has not lost any noticeable amount of oil. I changed the oil just before launching and brought the level just to the top of the hash marks on the dipstick. It is still at that level. It's still clean, too. This is new. In the past the oil was black and dirty even immediately after changing it.

The in-line fuel filter I added is working fine. The issue with the air in the filter has resolved itself. When I first installed the filter, I was unable to bleed out all of the air in the filter, which worried me. After running the engine for about two hours, all of the air in the filter disappeared without any problem with the operation of the motor. How this air got out and why it didn't cause any problems is a mystery but I'm happy with the resolution. Now that there is no air in the filter at all, I don't have any worries about air in the system.

I should also note that the engine now starts really well. It has always started pretty easily but often after sitting for more than a few days, particularly when cold, I'd need to crank it for 10 to 30 seconds to get it going. Now, it starts on the first compression stroke - even after sitting for days. I suspect this has a lot to do with the valves, which were not in great shape, but all the things I did are probably contributing.
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Old 20-06-2019, 19:20   #143
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Re: Yanmar SB12 Using Oil

^^ thanks for update, it's sounds like good news!

I agree your valves were probably the cause of hard cold starting. Delayed cold starting is almost always a symptom of low compression assuming battery, cabling and starter motor is in good condition. Crook valves would lower compression but the new rings must be helping as well

FWIW, poor electrics generally show up as reduced rpm before start while low compression shows up as a delayed start but with "normal" or even rpm during the start period.
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Old 20-06-2019, 19:55   #144
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Cool Re: Yanmar SB12 Using Oil

Yaay you've slain the dragon!
Mirrors our experience after recoing ysm8. Much easier starting & much slower to blacken oil with tiny consumption. Did you ever check oil pressure? Thanks for update, followed your mission with interest. Hope you have a good season.
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Old 21-06-2019, 08:05   #145
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Re: Yanmar SB12 Using Oil

Well, thank you guys for all your advise and help. This project would not have come out as well without the support I received through this forum. I'll post updates as the season progresses, but I think at this point the case is closed.
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